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Implications from these data A perception / production link appears to exist in the inhibition of stuttering. –Sensory and motoric forms of stuttering inhibition may be related. Inhibition is related directly to speech and appears to have a ‘gestural basis’. –Not just an auditory phenomenon. –Speech inputs are most effective sensory inhibitors May be explained by the engagement of mirror neurons.

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Mirror Neuron Systems Originally discovered in monkeys F5 area (considered an analog of Broca’s area). –In humans circuitry has been found to include: Inferior frontal gyrus Inferior parietal lobe Superior temporal sulcus Emotional centers including amygdala and insula Fire when goal-directed gestures are both perceived and produced. Are thought to be involved in development of: –Action and emotion recognition / empathy –Imitation –Language (Rizzolatti & Arbib, 1998) Motor theorists may see a role for mirror neurons in providing the neural substrate for linking speech perception and production (Liberman & Whalen, 2000).

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Mirror neurons and stuttering inhibition Choral speech / shadow speech are forms of direct imitation. –Mirror systems have been found to show highest levels of engagement during imitative tasks (e.g., Nishitani & Hari, 2002). Thus, it is likely that mirror neurons are engaged in the process of inhibiting stuttering. –It has been suggested that imitation is an act that humans perform fluently. Broca’s area has been found to be relatively deactivated during stuttering and normalized under choral speech. –Broca’s area is one of the primary mirror areas in mirror system. –One of the main roles of Broca’s areas is in producing fluent combinations of gestural sequences (Cooper, 2006)

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Mirror neurons and stuttering inhibition When perceiving other ‘second’ speech signals, the common goal is still speech. Therefore, the exogenous gestural sequence does not need to exactly match for stuttering to inhibited. However, the closer the linguistic match, the more stuttering is inhibited.

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Repetitions and prolongations as inhibitors Primary overt behaviors: –Repetitions and prolongations of sounds. –~80% recovery in children. Are these the problem or the solution to stuttering? –Interestingly, these behaviors are similar to motoric methods of inhibiting stuttering. Maybe they are ways to endogenously “self- imitate” to engage the mirror system and release the central block.

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A recent study We examined how altered auditory feedback differentially inhibits stuttering on during speech initiation and after speech has been initiated during 10s trials. Stuttering frequencies were examined in the first syllable and compared to stuttering frequencies on the next four syllables and 5 more syllables produced after the 5 second mark,

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Stuttering during speech initiation Stuttering was times more frequent on first syllable than all other syllables in NAF and AAF conditions.

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Implications Stuttering on the first syllable may be helping to inhibit further stuttering. Speech for people who stutter is difficult from a ‘cold start’ as no endogenous or exogenous speech feedback is present. AAF cannot aid directly in initiation but is powerful after speech is initiated. Choral speech, because it is exogenous can help inhibit stuttering during speech initiation.

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Procedure A two-minute recovery period was provided between stimulus tokens. The fluent and stuttered speech tokens were arranged using digram-balanced Latin square method and participants were randomly assigned to one order.